1. Field of the Invention
This invention relates to an improved accelerometer, and more particularly, to fluid resistors for making additional adjustments to a temperature compensated damping mechanism in the improved accelerometer.
2. Description of the Prior Art
An integrating accelerometer having a temperature compensated damping device incorporated therein is disclosed in U.S. Pat. No. 3,771,368, issued Nov. 13, 1973 to this inventor, and is incorporated herein by reference. This damping device has a helix member fixed on one end of a bellows and the opposite end of the bellows attached to an inner wall of a casing. This damping device provides a substantially constant damping coefficient by the expansion or contraction of the bellows in response to corresponding changes in the fluid volume in the casing due to temperature variations. The expansion or contraction of the bellows moves the helix member within the casing to change the length of the effective flow path. For example, the longer the effective flow path the greater the resistance to fluid flow. This longer path counteracts the decrease in viscosity due to a higher temperature. A lower temperature decreases the effective path length required to maintain a constant damping coefficient. This damping device is located within the accelerometer and is substantially effective in eliminating temperature variations over a wider range as an unwanted variable.
Additional adjustments to the above damping device are accomplished by the following: (1) varying the internal fluid amount to change the bellows stroke with temperature, and (2) changing the axial location of the helix.
As to the first method, fluid can be either added or subtracted from the casing. For example, by adding fluid, the bellows are compressed so that the effective flow path is increased. As to the second method, the volume can be adjusted by a piston device. For example, the piston can be moved into the fluid volume so that the bellows are compressed. This causes the helix to move axially thus changing the effective flow path.
The above methods of changing the effective flow paths to obtain constant damping over a range of temperatures have proved not to be as effective as desired.